Flame proofing of cellulosic materials



United States Patent 3,054,698 FLAME PROOFWG 0F CELLULOSIC MATERIALS George M. Wagner, Lewiston, N.Y., assignor to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Filed Nov. 21, 1960, Ser. No. 70,387

22 Claims. (Q1. 117-436) This invention relates to a process for the preparation of flame-retardant cellulosic materials and to the compositions produced thereby. More particularly, this invention relates to the treatment of cellulosic textiles with a solution containing a hydroxymethyl phosphonium chloride compound and a high softening point polyvinyl chloride resin to yield flame-retardant cellulosic textiles having markedly improved hand.

Numerous processes have been developed for treating cellulosic materials such as textiles with methylol-phosphorus polymers to render the textile flame-retardant, as exemplified by the disclosure of US. Patent No. 2,809,941, issued to Wilson A. Reeves and John D. Guthrie on October 15, 1957. When techniques such as these are employed, the treated fabric is flame-retardant when subjected to the standard char test, but under certain conditions the treated fabric will ignite, particularly after several washings of the treated cloth.

In another process it has been proposed to admix the methylol-phosphorus compounds disclosed by Reeves and Guthrie in the aforesaid patent with plasticized polyvinyl chloride resins having a softening point below about eighty degrees centigrade. Mixed polymers such as these also render the treated textile flame-retardant. However, frequent washings of the treated textile significantly aifect the flame retarding properties of the textile. Furthermore, the treated cloth has a relatively poor hand. In addition, cloth which has been treated with the aforesaid mixed polymers, becomes extremely stilf and boardy after repeated ironing. Additionally, when textiles are treated with the aforesaid mixed polymers, the fibers of the textile tend to swell, and remain in a swollen state after treatment, thereby significantly increasing the thickness of the cloth. This increase in thickness appears to adversely afiect the hand of the treated cloth.

It is an object of this invention to provide an improved method of preparing flame-retardant cellulosic materials.

A further object of the invention is to provide novel flame-retardant cellulosic materials.

Another object of the invention is to provide a method of improving the flame retardance and hand of cellulosic textiles.

Still another object of the invention is to provide novel cellulosic textiles which retain their flame-retarding properties after frequent washings.

Another object of the invention is to provide flameretardant cellulosic textiles having an improved hand, even after being subjected to fiequent ironing.

These and other objects of the invention, which will be apparent to those skilled the art, can be effected by the instant novel invention, which is described in detail hereinafter.

It has now been discovered that flame-retardant cellulosic materials having improved physical properties may be prepared by impregnating the cellulosic material with an aqueous resin dispersion containing a hydroxymethyl phosphonium chloride compound having the formula (CH OED RPCI, where R is as defined below, a water soluble cyclic nitrogen-containing compound, a water soluble tertiary alkyl amine, urea, and a polyvinyl chloride resin having a high softening point, and then drying and curing the resulting resin impregnated cellulosic material. When a cellulosic textile is treated in accord'ance with the instant invention, the resin impregnated textile has markedly improved hand, tear strength, tensile strength and flame retarding properties, when compared With textiles treated with resin compounds by techniques of the prior art.

Hydroxymethyl phosphonium chloride compounds suitable for use in the instant invention are those water soluble compounds having the formula (CH OH) RPCl, where R is hydroxymethyl, lower alkyls having between about one and about eight carbon atoms, and chlorinated lower alkyls having between about one and about eight carbon atoms. Typical examples of suitable water soluble hydroxymethyl phosphonium compounds are tetrakis(hydroxymethyl) phosphonium chloride, tris(hydroxymethyl) methyl phosphonium chloride, tris(hydroxymethyl) ethyl phosphonium chloride, tris(hydroxymethyl) butyl phosphonium chloride, tris(hydroxymethyl) octyl phosphonium chloride, tris(hydroxymethyl) chlorooctyl phosphonium chloride, and mixtures thereof. The phosphonium chloride may be used in monomer form or in a partially polymerized form, so long as it is still water soluble. For example, tetrakis(hydroxymethyl) phosphonium chloride may be heated to effect partial polymerization before dissolving in the aqueous solution.

Water soluble cyclic nitrogen-containing compounds suitable for use in the instant invention include triazines and dimethylol cyclic alkylene ureas. Typical examples of suitable triazines include methylol melamine, modified methylol melamine, such as the trimethyl ether of methylol melamine, triazones, and mixtures thereof. Typical examples of suitable cyclic alkylene ureas include dimethylol ethylene urea and dimethylol propylene urea.

Water soluble tertiary alkyl amines which are suitable for use in the instant invention include triethylamine, triethanolamine, triisopropanolamine, and the like.

Polyvinyl chloride resin suitable for use a a component of the novel flame-proofing composition are polyvinyl chloride resins having a softening point between about one hundred and seventy and about two hundred degrees centigrade. The polyvinyl chloride resin is preferably unplasticized and substantially pure, but may contain minor proportions of other monomers such as polyvinyl acetate, acrylics and plasticizers, but the proportions of these ingredients in the polyvinyl chloride resin should be less than those proportions that will reduce the softening point of the resulting mixture to below about one hundred and sixty degrees centigrade. The polyvinyl chloride resin is preferably employed as an aqueous dispersion or emulsion containing between about forty-five and about fifty-five percent by weight of polyvinyl chloride resin in the dispersion.

Urea is also employed as a component of the flameproofing composition in the proportions defined below.

The approximate proportions of the aforesaid components used in preparing the aqueous resin dispersion or emulsion are as follows:

Any cellulosic material such as cotton, rayon, ramie, ute, wool, paper, cardboard and the like may be treated m accordance with the instant invention, but the inven- 3 tion is particularly effective when applied to the treatment of cellulosic textiles, since the treated textiles have a markedly improved hand as well as flame retarding properties.

In preparing the aqueous dispersion or emulsion/the aforesaid components are admixed with sufiicient water to yield an aqueous resin dispersion or emulsion containing between about forty-five and about eighty percent,

and preferably between about fifty and about seventy percent total solids by'wcignt. The term total solids as used throughout the description'and claims, is intended to include both the solids that are dissolved in the aqueous component, as well as those solids which are colloidally dispersed or otherwise dispersed in the aqueous dispersion or emulsion. The word dispersion, as used throughout the description and claims, is intended to include the dispersion and/or emulsion that results from admixing the above defined hydroxymethyl phosphonium chloride compound, the cyclic nitrogen-containing compound, the water soluble tertiary alkyl amine, urea, polyvinyl chloride resin and water in the proportions defined above. Greater or lesser proportions of the aforesaid components may be employed so long as the concentration of total solids in the aqueous dispersion is sufiicient .to provide an adequate resin add-on for the cellulosic material being treated.

The cellulosic material is impregnated with the aque ous resin dispersion by padding, by spraying, by rolling, or by other impregnating techniques well known to the art. It is preferred to immerse the cellulosic material in the aqueous dispersion until the cellulosic material is completely saturated, and then pass the cellulosic material through squeeze rolls to remove resin dispersion in excess of that amount necessary to saturate the cellulosic material.

The saturated cellulosic material is then subjected to conditions of temperature and time, sufficient to effect drying of the saturated cellulosic material and curing of the resin. Drying and curing can be effected by any commercially feasible technique. For example, drying of the cellulosio material can be effected in a conventional forced hot air oven wherein the saturated cellulosic material is heated at a temperature between about eighty and about one hundred andtwenty degrees centigrade for between about two and about four minutes. Curing of the dried cellulosic material can be effected in the same apparatus by heating the dried 'cellulosic material to a temperature of between about one hundred and forty and about one hundred and sixty degrees centigrade, for between about two and about four minutes. If desired, curing of the dry, treated cellulosic material can be effected in an infrared oven at a temperature between about five hundred and about seven hundred degrees Fahrenheit, for a period between about five and about twelve seconds.

After curing, the resin impregnated cellulosic material is preferably subjected to a scouring step in order to remove unpolymerized resin. For example, scouring can be effected by immersing the cured cellulosic material in an aqueous solution containing about 0.2 percent by weight of soap and about 0.2 percent by weight of sodium carbonate. After immersing the. resin impregnated eellulosic material in the solution, it is then dried as described above.

The proportion of resin added to the cellulosic material by the aforesaid novel technique is generally between about fifteeen and about thirty-five percent by weight of the cellulosic material. This proportion of resin is referred to throughout the description and claims as resin add-on. The resin formed on the cellulosic material by the instant novel process is the reaction product of the non-aqueous components of the aqueous resin dispersion, i.e., the hydroxymethyl phosphonium chloride compound, the cyclic nitrogen-containing compound, the water-soluble tertiary alkyl amine, urea, and the high softening point polyvinyl chloride fresin. When the aqueous resin dispersion contains the resin forming ingredients in the proportions defined above, the resulting resin which impregnates the cellulosic material is the reaction product of hydroxyrnethyl phosphonium chloride compound in a proportion equivalent to between about ten and about sixty percent, the cyclic nitrogen-containing compound in a proportion equivalent to between about five and about forty percent by weight, the water-soluble tertiary alkyl amine in a proportion equivalent to between about one and about twenty percent by weight, urea in a proportion equivalent to between about five and about forty percent by weight, and the high softening point polyvinyl chloride resin in a proportion equivalent to between about ten and about seventy percent by weight of the resin forming in gredients.

Cellnlosic materials treated in accordance with the instant invention have improved flame retarding properties, which are retained even after the treated cellulosic material is contacted with water and other solvents. For example, when cellulosic textiles are treated in accordance Withthe instant invention, the textile is not only flame-retardant, but also has a markedly improved hand, that is, the textile is soft and flexible, and these properties are retained after repeated washings and ironings.

The following examples are presented to define the invention more fully without any intention of being limited thereby. All parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 'An aqueous dispersion was prepared from the following components in the following proportions.

. Component: Parts by weight Tetrakis (hydroxymethyl) phosphonium chloride 17.7

Tn'ethanolamine 3.5

Trimethylolmelamine 10.4

Urea 10.4 Polyvinylchloride resin (aqueous dispersion containing resin solids) 1 45.0

Water 53.5

1 Softening point of polyv' ylchloride resin was one hundred and eighty degrees Centigrade.

The resulting aqueous dispersion contained forty-six percent solids.

A nine-ounce battle-ax fabric of the type conventionally used for Work garments, was immersed in the above-described aqueous dispersion, then passed through squeeze rolls to remove excess liquid, and then dried at a temperature of two hundred and fifty degrees Fahrenheit. The 'dried, treated fabric was then placed in an infrared oven for about ten seconds at a temperature of about seven hundred degrees Fahrenheit to effect curing of the resin. The resin treated fabric was then scoured by immersing it in an aqueous solution containing 0.2 percent non-ionic detergent and 0.2 percent sodium carbonate. After scouring, the fabric was dried. The resin add-on-of the resin treated fabric after scouring and drying was 33.6 percent. The tensile strength of the treated fabric, as determined in accordance with Federal Specification CCC-T19lb#5 100, using aScott tensile tester, was one hundred and thirty-five pounds, as compared to a tensile strength of one hundred and thirty for the untreated fabric. a

The resin treated fabric was subjected to the standard char test. The char test was carried out in accordance with the American Association of Textile Chemists and colorists, Test AATC 34-4952. In this test, a strip of cloth to be tested is secured on each of its long sides in a vertical position, leaving an exposed area of approximately ten inches by two and one-quarter inches. A Bunsen burner is positioned ,below the bottom of the cloth so that the top of the burner is about three-quarters of an inch from the cloth. The burner produces a flame which is about one and one-half inches high. The flame is produced by burning natural gas in the absence of air. The cloth is exposed to the flame for a period of twelve seconds, and the flame is then turned off. The cloth is then removed from the securing means and a weight is 6 between about forty-five and about eighty percent by weight of water, between about six and about twenty percent by weight of a hydroxymethyl phosphonium chloride compound having the formula (CH OH) RPC1,

attached to one Side of the char, the Weight being q where R is selected from hydroxymethyl, lower alkyls 316m PF 0f the teal" Strength f the 010thhaving between one and about eight carbon atoms, and The pp slde of the cloth is then pulled to produce chlorinated lower alkyls having between one and about a tea! along the chaf- The length of the tear is then eight carbon atoms, between about three and about twelve measured F determine h char in inchespercent by weight of a member of the group consisting of The E5111 trehted tabl'lc had a y good hand, and had triazines and dimethylol cyclic alkylene ureas, between a char of lhches y h Standard char test- After about one and about four percent by weight of a watertwenty a launderlpgs, the treatftd cloth 'f a soluble tertiary alkyl :amine, between about three and char of 3.3 1nches; after thirty commercial launderings, about twelve percent by Weight f urea and between f a char of lnches- The tr?ated th after h about seven and about twenty-five percent by weight of sub ected to these extreme laundering cond1t1ons,st1llrea polyvinyl chloride resin having a ft i point h tamed lts very good hand, and was soft, flexible and tween about one hundred and seventy and about two crease reslstanthundred degrees centigrade, and drying and, curing the EXAMPLES treated cellulosic material.

The procedure of Example 1 was repeated, employing The P of claim 2 wherein Said hYdIOXYIIIEthYI polyvinylchloride resins of various softening points, as PhOSPhOBiUm fihlol'ide is Y Y Y P indicated in the table below. Phonlum chl'orlde- Table Example 2 3 4 5 6 7 Softening point of polyvinyl chloride, 0 40-50 70-80 110-120 140-150 180-200 190-200 Percent resin add-on after cure and scour 30 80 31 30 Gurley stiffness, mg 330 620 540 820 540 420 Thickness, mills 34.2 32.5 33.4 31.5 31.9 31.2 Hand rating of treated cloth (1=best, 6=worst):

Observer A 5 4 6 3 2 1 Observer B 3 4 5 6 2 1 Observer O 3 5 4 6 2 1 Examples 6 and 7 show the improved results that are 4. The process of claim 2 wherein said cellulosic maobtained by the technique of the instant novel invention, terial is a cellulosic textile. while Examples 2, 3, 4 and 5 show the results obtained 5. The process of claim 2 wherein the resin add-0n of by procedures of the prior art. The cloths produced in the treated cellulosic material after curing is between Examples 6 and 7 had a superior hand as compared to the about fifteen and about thirty-five percent by weight of treated cloths produced in Examples 2 to 5, and the cloths the cellulosic material. of Examples 6 and 7 also were significantly less bulky 6. The process of claim 2 wherein drying of the celluthan the cloths of Examples 2, 3 and 4. Although the losic material impregnated with said aqueous dispersion stiffness of the cloth produced in Example 2 (where alow is effected at a temperature between about eighty and softening point polyvinyl chloride resin was employed), about one hundred and twenty degrees centigrade for a was less than that obtained with the high softening point period between about two and about four minutes, and polyvinyl chloride in Examples 6 and 7, nevertheless the curing of the resulting material is effected at a temperature thickness or bulkiness of the cloth produced in Example 2 between about one hundred and forty and about one was much greater than that obtained in Examples 6 and 5 hundred and sixty degrees centigrade for between about 7, and as a result, the hand of the treated material protwo and about four minutes. duced in Examples 6 and 7 was markedly superior to that 7. A process for preparing a flexible, flame retardant of Example 2. cellulosic textile which comprises impregnating the cellu- It will be recognized by those skilled in the art that losic textile to be treated with an aqueous dispersion convarious modifications within the invention are possible, taining between about forty-five and about eighty persome of which have been referred to above. Therefore, cent by weight of water, between about six and about I do not wish to be limited except as defined by the aptwenty percent by weight of tetrakis(hydroxymethyl) pended claims. phosphonium chloride, between about one and about four I claim: percent by weight of triethanolamine, between about 1. A process for preparing a flame-retardant, cellulosic three and about tWelVe Percent y Weight of trimethylmaterial which comprises impregnating the cellulosic maolmelamine, bE W about three and about tWfilVe P terial to be treated with an aqueous dispersion of a hycent by weight of urea, and between about seven and droxymethyl phosphonium chloride compound having the about twenty-five percent by weight of a polyvinyl chloformula (CH OH) RPCl, where R is selected from hyride resin having a softening point between about one droxymethyl, lower alkyls having between one and about 5 hundred and seventy and about two hundred degrees eight carbon atoms, and chlorinated lower alkyls having centigrade, and drying and curing the treated cellulosic between one and about eight carbon atoms, a member of material. the group consisting of triazines and dimethylol cyclic 8. The process of claim 7 wherein the resin add-on of alkylene ureas, a water-soluble tertiary alkyl amine, urea, the treated cellulosic material after curing is between and a polyvinyl chloride resin having a softening point about fifteen and about thirty-five percent by weight of between about one hundred and seventy and about two the cellulosic textile. hundred degrees centigrade, and drying and curing the 9. The process of claim 7 wherein the cellulosic textile treated cellulosic material. impregnated with said aqueous dispersion is dried at a 2. A process for preparing a flame-retardant, cellulosic temperature between about eighty and about one hundred material which comprises impregnating the cellulosic maand tweny degrees centigrade, for a period between about terial to be treated with an aqueous dispersion containing two and about four minutes, and curing of the resulting 10. A flame retardant cellulosic material comprised of p a cellulosic material impregnated with a resinous material comprised of the reaction product of a hydroxymethyl phosphonium chloride compound having the formula (CH OH) RPCl, where R is selected from bydroxymethyh'lower alkyls having between one and about eight carbon atoms, and chlorinated lower alkyls having between one and abou-t eight carbon atoms, a member of the group consisting of triazines and dimethylol cyclic alkylene ureas, a water-soluble tertiary allcyl amine, urea, and a polyvinyl chloride resin having a softening point between about one hundred and seventy and about two hundred degrees centigrade.

11. A flame retardant cellulosic material comprised of a cellulosic material impregnated with a resinous material, said resinous material being thetreaction product formed from resin forming ingredients comprised of a hydroxymethyl phosphonium chloride compound having the formula (CH OH) RPCl, where R is selected from by droxymethyl, lower alkyls having between one and about eight carbon atoms, and chlorinated lower alkyls-having between one and about eight carbon atoms, in atpropon tion equivalent to between about ten and about sixty percent by weight, a member of the group consisting of triazines and dimethylol cyclic alkylene ureas in a proportion equivalent to between about five and about forty percent by weight, a water-soluble tertiary alkyl amine in a proportion equivalent to between about one and about twenty percent by weight, urea in a proportion equivalent to between about five and about forty percent by weight, and a polyvinyl chloride resin having a softening point between about one hundred and seventy and about two hundred degrees centigrade ina proportion equivalent to between about ten and about seventy percent by weight of the resin forming ingredients.

12. The flame retardant cellulosic material of claim 11 wherein said hydroxymethyl phosphonium chloride compound is tetrakis(hydroxymethyl) phosphonium chloride.

13. The flame retardant cellulosic material of claim 11 wherein said cellulosic material is a cellulosic textile.

14. The flame retardant cellulosic material of claim 11 wherein the resin add-on is between about fifteen and about thirty-five percent by weight of the cellulosic ma terial.

15. A flame retardant cellulosic material comprised of a cellulosic material impregnated with a resinous material, said resinous material being the reaction product formed from resin forming ingredients comprised of tetrakis(hydroxymethyl) phosphonium chloride in a proportion equivalent to between about ten and about sixty percent by weight, trimethylol melamine in a proportion equivalent to between about five and about forty percent by weight, triethanol amine in a proportion equivalent to between about one and about twenty percent by weight, urea in a proportion equivalent to between about five and about forty percent by weight, and a polyvinyl chloride resin having a softening point between about one hundred and seventy and about two hundred degrees centigrade in a proportion equivalent to between about ten and about seventy percent by weight of the resin forming ingredients.

16. The flame retardant cellulosic material of claim 15 wherein said cellulosic material is a cellulosic textile.

17. The flame retardant cellulosic material of claim 15 wherein the resin add-on is between about fifteen and about thirty-five percent by weight of said cellulosic niaterial.

18. The flame retardant cellulosic material of claim 15 wherein said polyvinyl chloride resin has a softening point between about one hundred and seventy and about two hundred degrees Centigrade.

19. A flame retardant cellulosic textile comprised of i=3 a cellulosic textile impregnated with a resinous material, said resinous material being the reaction product formed fromresin forming ingredients comprised of tetralcis(hydroxymethyl) phosphonium chloride in a proportion equivalent to between about ten and about sixty percent by weight, trimethylol melamine in a proportion equivalent to between about five and about forty percent by weight, triethanol amine in a proportion equivalent to between about one and about twenty percent by weigh-t, urea in a proportion equivalent to between about five and about forty percent by weight, and a polyvinylchloride resin having a softening point in the range between about one hundred and seventy and about two hundred degrees centigrade in a proportion equivalent to between about ten and about seventy percent by weight of said resin forming ingredients, wherein the resin add-on is between about twenty and about thirty-five percent by weight of said flame retardant cellulosic material. 7

20. A cellulosic material treating composition comprised of a hydroxymethyl phosphonium chloride compound having the formula (CH OH) RPCl, where R is selected from hydroxymethyh lower alkyls having between one and about eight carbon atoms, and chlorinated lower alkyls having between one and about eight carbon atoms, a member of the group consisting of triazines and dimethylol cyclic alkylene ureas,a water-soluble tertiary alkyl amine, urea, a polyvinyl chloride resin having a softening point between about one hundred and seventy and about two hundred degrees centigrade, and water.

21. A cellulosic material treating composition comprised of an aqueous dispersion containing between about six and about twenty percent by weight of a hydroxymethyl phosphonium chloride compound having the formula (CH- OH) RPCI, where R is selected from hydroxymethyl, lower alkyls having betweentone and about eight carbon atoms, and chlorinated lower alkyls having between one and about eight carbon atoms, between about three and about twelve percent by weight of a member of the group consisting of triazines and dimethylol cyclic alkylene areas, between about one and about four percent by weight of a water-soluble tertiary alkyl amine, between about three and abouttwelve percent by weight of urea, between about seven and about twenty-five percent by weight of a polyvinyl chloride resin having a softening point between about one hundred and seventy one hundred and seventy and about two hundred degrees centigrade, and between about forty-five and about eighty .percent by weight of water.

References:Cited in the file of this patent UNITED STATESPATENTS Stilbert et al July 27, 1954 Reeves et a1 Oct. 22, 1957 OTHER REFERENCES Guthrie, J. D.; Drake, G. L., In; and Reeves,Wilson: Application of the THPC Flame-Retardant Process to Cotton Fabrics, Proceedings of the American Assoc. of Textile Chemists and Colorists, May 9, 1955, pp. 2-5.

Skinner, S. 1., and Bolam, S. E: Fire-Resistant Properties of PVC and Related Polymers, Rubber and Plastics Age, March 1956, page 171; 

7. A PROCESS FOR PREPARING A FLEXIBLE, FLAME-RETARDANT CELLULOSIC TEXTILE WHICH COMPRISES IMPREGNATING THE CELLULOSIC TEXTILE TO BE TREATED WITH ANAQUEOUS DISPERSION CONTAINING BETWEEN ABOUT FORTY-FIVE AND ABOUT EIGHTY PERCENT BY WEIGHT OF WATER, BETWEEN ABOUT SIX AND ABOUT TWENTY PERCENT BY WEIGHT OF TETRAKIS (HYDROXYMETHYL) PHOSPHONIUM CHLORIDE, BETWEEN ABOUT ONE AND ABOUT FOUR PERCENT BY WEIGHT OF TRIETHANOLAMINE, BETWEEN ABOUT THREE AND ABOUT TWELVE PERCENT BY WEIGHT OF TRIMETHYLOLM,ELAMINE, BETWEEN ABOUT THREE AND ABOUT TWELVE PER CENT BY WEIGHT OF UREA, AND BETWEEN ABOUT SEVEN AND ABOUT TWENTY-FIVE PERCENT BY WEIGHT OF A POLYVINYL CHLORIDE RESIN HAVING A SOFTENING POINT BETWEEN ABOUT ONE HUNDRED AND SEVENTY AND ABOUT TWO HUNDRED DEGREES CENTIGRADE, AND DRYING AND CURING THE TREATED CELLULOSIC MATERIAL. 